Function dlartg_

numpy/linalg/lapack_lite/f2c_d_lapack.c:23485–23646

Subroutine */

} /* dlarfx_ */

/* Subroutine */ int dlartg_(doublereal *f, doublereal *g, doublereal *cs,
	doublereal *sn, doublereal *r__)
{
    /* System generated locals */
    integer i__1;
    doublereal d__1, d__2;

    /* Local variables */
    static integer i__;
    static doublereal f1, g1, eps, scale;
    static integer count;
    static doublereal safmn2, safmx2;

    static doublereal safmin;


/*
    -- LAPACK auxiliary routine (version 3.2) --
    -- LAPACK is a software package provided by Univ. of Tennessee,    --
    -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
       November 2006


    Purpose
    =======

    DLARTG generate a plane rotation so that

       [  CS  SN  ]  .  [ F ]  =  [ R ]   where CS**2 + SN**2 = 1.
       [ -SN  CS  ]     [ G ]     [ 0 ]

    This is a slower, more accurate version of the BLAS1 routine DROTG,
    with the following other differences:
       F and G are unchanged on return.
       If G=0, then CS=1 and SN=0.
       If F=0 and (G .ne. 0), then CS=0 and SN=1 without doing any
          floating point operations (saves work in DBDSQR when
          there are zeros on the diagonal).

    If F exceeds G in magnitude, CS will be positive.

    Arguments
    =========

    F       (input) DOUBLE PRECISION
            The first component of vector to be rotated.

    G       (input) DOUBLE PRECISION
            The second component of vector to be rotated.

    CS      (output) DOUBLE PRECISION
            The cosine of the rotation.

    SN      (output) DOUBLE PRECISION
            The sine of the rotation.

    R       (output) DOUBLE PRECISION
            The nonzero component of the rotated vector.